Your pictures must be on your computer (downloaded from your digital camera, most likely).

On the "Post an Item" and the "Edit Item" pages, you will see fields where you can click "Browse" to locate the picture you want to add. Once you select the picture(s), make sure you click "Add".

A buyer/seller didn't treat me right!

If you're one of the 0.0003% of users having a bad experience, shame on you for not being more careful! ;-) All transactions are between the buyer and the seller, and so is any fixing of bad experiences. And law enforcement if necessary. Please don't complain on the site about bad sellers or buyers. And be more careful next time. Test the item before you buy!

Why did my item get flagged?

Good question. Since it's done by the community, we can't tap their brains directly to find out. But you might try looking at the FAQ on flagging and see if any of the reasons might apply to you.

My item isn't showing up?

Items post immediately to your "My Items" and to the front page, but take a few minutes to appear in the categories and the search.